The East Anglian economy could generate an extra £9bn - if transport chiefs invest £660m in its rail infrastructure, regional leaders claim.

New Anglia Local Enterprise Partnership and the county councils in Norfolk, Suffolk and Essex are calling on the government to invest in the network in order to bring big economic benefits.

The Great Eastern Main Line (GEML) Rail Taskforce has written to transport secretary Grant Shapps and chancellor of the exchequer Rishi Sunak calling on them to back the business case for the works, which will be finalised in the autumn.

The proposed package of improvements could create 5,100 new jobs in Norwich, 5,400 in Ipswich, 10,000 in Colchester, 8,400 in Chelmsford and 3,700 in Southend, says the group. Over the next 20 years, 320,000 new homes - including garden cities - are planned for the fast-growing region.

Taskforce chair Giles Watling MP said: “Investing in the Great Eastern Main Line not only brings significant benefits to our region through the creation of new jobs, development land for homes, and provides more opportunities for our residents, but it also supports national productivity and unlocks further funding for Government to invest across the UK.”

There was “a strong and compelling case" that investment in the GEML could generate up to £9.3bn in economic benefits across the region once wider population concentrations and productivity benefits had been included, said Mr Watling.

“The financial benefit of journey time savings is estimated at £6m annually. Over a 30-year period, journey time savings would equate to a total of £179m," he said.

“The total investment cost is estimated to be in the region of £660m, with the Summary Business case showing a benefit to cost ratio of 5.6 – which represents very high value for money and generating £5.60 of economic benefits for every pound of investment.”